Hepatic portal venous gas in the case of superior mesenteric artery thrombosis in a young adult‐case report

Abstract Hepatic portal venous gas is diagnosed via computed tomography due to unusual imaging features. HPVG when linked with pneumatosis intestinalis has a high mortality rate and required urgent intervention. We present a case of a 26‐year‐old young adult with superior mesenteric artery thrombosis who presented with severe abdominal pain. On imaging, HPVG and pneumatosis intestinalis were seen owing to the urgent intervention of the patient. The reliable interpretation of the imaging findings along with quick intervention led to a favorable outcome in our case. Herein, we present a thorough review of the imaging findings of HPVG to make a reliable diagnosis when presented with such a case.


Abstract
Hepatic portal venous gas is diagnosed via computed tomography due to unusual imaging features. HPVG when linked with pneumatosis intestinalis has a high mortality rate and required urgent intervention. We present a case of a 26-year-old young adult with superior mesenteric artery thrombosis who presented with severe abdominal pain. On imaging, HPVG and pneumatosis intestinalis were seen owing to the urgent intervention of the patient. The reliable interpretation of the imaging findings along with quick intervention led to a favorable outcome in our case. Herein, we present a thorough review of the imaging findings of HPVG to make a reliable diagnosis when presented with such a case.

K E Y W O R D S
hepatic portal venous gas, intestinal perforation, Pneumatosis intestinalis, superior mesenteric artery (SMA) thrombosis temperature of 98 F, and SpO2 93%. Abdominal examination revealed marked abdominal tenderness diffusely. In addition, he had guarding and rigidity present.
Laboratory examination showed the following: Following the laboratory examination, a CT scan of the abdomen was done.

| CT finding of the patient
Noncontrast and contrast CT of abdomen and pelvis were done, which demonstrate linear branching air attenuating areas (HU-998) in both lobes of liver involving periphery and in the region of portal venous branches, these features are suggestive of portal venous gas ( Figure 1). Postcontrast study shows near total non-enhancing filling defect in superior mesenteric artery starting from approximately 2 cm distal to its origin ( Figure 2). There was thinning of bowel loops in pelvic region (probably small bowel loops) with hypoenhancing walls and multiple round cystic air attenuating areas within the bowel walls demonstrating pneumatosis intestinalis ( Figure 3). Minimal free fluid is noted in pelvic peritoneal cavity.

| IMAGING DIAGNOSIS
Superior mesenteric artery thrombosis leads to the bowel ischemia along with pneumatosis intestinalis and hepatic portal venous gas.

| DISCUSSION
Hepatic portal venous gas (HPVG) is a rarely described form of pneumatosis and refers to gas within the portal vein. 4 Radiologically, linear branched radiolucencies that reach the liver's edge within 2 cm are referred to as HPVG. 2 The first case of HPVG was described in 1955 by Wolf and Evans. 5 Mucosal damage, bowel distension, and sepsis caused by gas-forming bacteria are the three possible mechanisms of HPVG. A necrotic bowel was present in more than two-thirds of patients with hepatic portal venous gas. Pneumatosis intestinalis (PI), subserosal and submucosal gas-filled cysts in the digestive tract, is frequently accompanied by hepatic portal venous gas. 2,6,7 Numerous fatal and non-fatal diseases and disorders, including intestinal necrosis, total or partial bowel obstruction, intraperitoneal abscess, ulcerative colitis, gastric ulcer, Crohn disease, trauma, endoscopic procedure complications, and diverticulitis, are associated with HPVG. The main cause of HPVG is ischemic bowel with subsequent intestinal necrosis. 2 HVPG is a rare occurrence, and it is challenging to treat. 6 It is even more challenging and has higher mortality when it is associated with bowel necrosis as reported by Kinoshita et al. 5 In our case, HPVG along with Pneumatosis Intestinalis manifested as a result of bowel ischemia due to superior mesenteric artery (SMA) thrombosis, which later caused the necrosis.
HVPG is diagnosed radiologically using ultrasound or computed tomography (CT). 5 However, CT has higher sensitivity for its diagnosis among all and is used as gold standard for its diagnosis. 2,5 Ultrasound shows either echogenic particles flowing within the portal vein or poorly defined, echogenic patches within the hepatic parenchyma, mostly in nondependent part. 5 It is possible to dynamically image the centrifugal flow of portal gas to the hepatic periphery using color Doppler flow imaging, differentiating it from biliary gas. 2 In CT imaging, HPVG appears as branching lucencies that extend to within 2 cm of the liver capsule, primarily in the anterior-superior portion of the left lobe. As opposed to biliary gas (pneumobilia), which is linked to air in the liver's center but does not reach as far toward the liver capsule as does HPVG (air in HPVG extends to a less than 2 cm from the liver capsule, whereas in pneumobilia it does not reach to that extent), pneumobilia is characterized by air within the liver's central region. 8 HPVG was diagnosed using CT imaging in our case, which showed shows near total nonenhancing filling defect in superior mesenteric artery starting from approximately 2 cm distal to its origin ( Figure 2). It was also associated with the finding of PI seen as was thinning of bowel loops in pelvic region (probably small bowel loops) with hypoenhancing walls and multiple round cystic air attenuating areas within the bowel walls ( Figure 3).
Treatment of HPVG mostly depends upon the underlying cause. It also depends on the presence or absence of peritonitis or intestinal perforation, as well as the patient's general condition, as they are the primary characteristics that direct clinicians in their therapeutic strategy. 9 Our patient's condition was deteriorating. He was resuscitated with intravenous fluid and antibiotics. With the diagnosis of the bowel ischemia due to SMA thrombosis, he underwent emergency explorative laparotomy and resection and anastomosis was done ( Figure 4). Fortunately, he became stable and improved after the surgery.

| CONCLUSION
HPVG is not always a sign of a fatal intraabdominal pathology; however, it may be seen in such kind of illness. It can be diagnosed by Ultrasound or CT scan (which is considered as gold standard for its diagnosis). The treatment depends on the underlying pathology as in our case it was due to bowel ischemia resulting from SMA thrombosis. He had to undergo surgical treatment due to the deteriorating clinical status. It is vital for a clinician to recognize when HPVG can be life-threatening and require intervention.